The Woracle

Hy-what? Finding it hard to keep all those hypersonics programmes straight?

After all, the US Air Force Research Laboratory's Boeing X-51A waverider, powered by Pratt & Whitney Rocketdyne's SJX61 scramjet, is the just latest in a long line. Here is a quick guide to the various recent and current research efforts aimed at air-breathing vehicles capable of speeds exceeding Mach 5.

[NOTE - I updated this on 10/15/07 and will try to keep it up to date.]

DARPA's annual tech-fest has caused a stir in the blogosphere with the first appearance of a model of the HTV-3X demonstrator being designed by Lockheed Martin's Skunk Works under the Falcon hypersonic technology programme.

Bill Sweetman broke the story on AvWeek's Ares blog, and Sharon Weinberger weighed in on Wired's Danger Room. Hopefully Bill won't mind me stealing his picture...

But what's this about the Blackswift?

The internet has been abuzz with stories about a new US space weapons programme, all based on an erroneous report in the Washington Post about one of my favourite DARPA projects - the Falcon hypersonic cruise vehicle technology demonstrator.

Falcon has been around for yonks, but the Post managed to mangle the wording of the House-Senate conference report on the 2008 defence budget. This zeroed out the US Navy's Conventional Trident Modification programme to convert nuclear missiles into precision bombers, but provided $100 million for a new Prompt Global Strike programme. The money came from CTM and the US Air Force's Common Aero Vehicle project to develop a conventional-warhead ballistic missile re-entry vehicle - but is not going to Falcon, as the Post reported.

DARPA has just awarded Lockheed Martin's Skunk Works a $40.8 million contract to build two HTV-2 hypersonic technology vehicles to be flight-tested in 2009 under the Falcon programme. This gives me a good excuse to update my Short Guide to Hypersonics Programmes.

The HTV-2 is an unpowered, unmanned, expendable vehicle to demonstrate high lift/drag aerodynamics and high-temperature materials for sustained hypersonic cruise, and is intended a stepping stone to the powered, reusable HTV-3X, aka Blackswift.

When a test flight lasts only minutes and ends in a fiery plunge into the ocean, you want to make sure the radios work - to ensure telemetry data is safely sent to the ground. So Boeing is testing the antennas for the US Air Force Research Laboratory's X-51A Scramjet-Waverider hypersonic demonstrator in the anechoic chamber at Edwards AFB.

Powered by a Pratt & Whitney Rocketdyne scramjet that uses the fuel to cool itself, the first X-51A is scheduled to fly in August 2009 - dropped from a B-52 50,000ft over the Pacific, boosted to Mach 4.7, where the scramjet will light and run for 5min, accelerating the vehicle to Mach 6.7 before the tanks run dry and it plunges into the ocean. Those radios had better work.

It ended up in a hangar covered in bird crap, that's what. A remnant of an unhappy time in NASA's recent history, the Orbital Sciences-built X-34 was photographed by Ashley Wallace in storage at Edwards AFB in California. The X-34 was built as a flying testbed to demonstrate technology for future low-cost reusable launch vehicles.

(Picture by Ashley Wallace, from airliners.net)

The unmanned X-34 was intended to be air launched from Orbital's Lockheed L-1011 mothership and accelerated to Mach 8 by a NASA-built oxygen/kerosene rocket engine. The vehicle was designed to land on a runway and fly up to 25 times to test composite structures, resuable propellant tanks and thermal protection systems, and autonomous flight operations.

Orbital got as far as captive-carry tests on the L-1011 before the X-34 was cancelled in 2001, along with Lockheed Martin's mightily ambitious X-33 single-stage-to-orbit RLV technology demonstrator (video). Spiralling costs and changes in NASA's RLV thinking were blamed. Two completed X-34s and parts for the third were transferred to the US Air Force.

Blackswift may have emerged out of Lockheed Martin Skunk Works' Falcon hypersonic technology demonstration, but DARPA is looking for competitive bids to design and build the unmanned demonstrator, issuing this solicitation in early March:

"The Tactical Technology Office (TTO) of the Defense Advanced Research Projects Agency (DARPA) is soliciting proposals to develop an extended duration hypersonic testbed known as Blackswift. The Government seeks development of a reusable hypersonic testbed that utilizes an integrated air-breathing propulsion system.

The Blackswift flight test program is pursing development and demonstration of near-term (2012) capability. The Government is soliciting original conceptual flight testbed design approaches from the aerospace community that meet or exceed these objectives."